Thesis_October_15_2014_Richard_Nielsen_FINAL VERSION
1. Implementation of a Sustainable Process for Waste Disposal and Omega-3 Fatty Acid
Production
Richard Barton Nielsen
A Thesis in the Field of Biotechnology
for the degree of Master of Liberal Arts in Extension Studies
Harvard University
November 2014
3. Abstract
Omega-3 fatty acids are popular nutritional supplements with a high global demand.
Currently, the primary method for harvesting omega-3’s is by extracting them from fish.
This practice is damaging to marine ecosystems and to the economic and social
infrastructures that support the fishing industry. Additionally, omega-3’s extracted from
fish are more likely to be contaminated with pollutants (e.g., mercury) and are not
suitable for vegetarian diets. Identifying alternative sources for omega-3’s are important
to decrease the negative impacts associated with utilizing fish. Omega-3 fatty acids can
be obtained from a variety of sources, including farmed microalgae. Exploiting
microalgae for omega-3 fatty acids would relieve some pressures placed on global fish
stocks. Farming microalgae also provides a healthier, more pure form of omega-3’s.
The primary objective of this project is to create a biotechnological system that
optimizes the use of microalgae farming for the production of omega-3 with
eicosapentaenoic acid (EPA). Our investigations generated previously unreported data
necessary for selecting a microalgae species, Nannochloropsis oculata, and for optimizing
its ability to produce omega-3 with EPA. Experiments testing optimal growth conditions
(e.g., temperature, CO2 concentration, light availability) and pest control methods were
conducted. Our results directed the construction of an algae farming process that
efficiently produces Nannochloropsis oculata with a high concentration of omega-3 with
EPA.
4. The second objective of this project is to build a sustainable system to support the
farming of Nannochloropsis oculata. Increasing the concentration of CO2 in the water
used for microalgae farming increases the growth rate of microalgae. Therefore,
identifying a stable source of CO2 is necessary and, as we have reported, widely available
in the form of biological waste. Transforming this waste into CO2 is possible by using
plasma gasification. Numerous benefits are derived through the use of plasma
gasification technology for generating CO2. Air pollutants are destroyed in the process
and landfill disposal is greatly reduced. Negative environmental and human health
impacts are significantly less than those of current waste disposal activities (landfilling
and incineration).
The successful implementation of our proposed waste-algae processing system for
the generation of omega-3 fatty acids shines light on a sustainable process that can
provide vast global benefits for the environment, economy, agriculture, and society.
5. v
Acknowledgments
My successful journey through the thesis process would not have been possible
without Dr. Ramon Sanchez. Ramon, you were a true guide and teacher who I hope to
continue learning from. You truly opened my eyes allowing me to understand the huge
potential that merging biotechnology and sustainability can have. I’ve learned that
sustainability is synonymous with efficiency. A sustainable system is efficient and the
use of biotechnology is a perfect medium to build such systems. The possibilities are
endless…
Encouragement to perceiver and finish my project came to me from numerous family
and friends. Thank you to dad, Richard, and my mom, Kathryn. Both are educators with
graduate degrees who gave me something to look up to. Dad, I wish you were here to
witness the completion of my project. Mom, I’m afraid to think of where I would be
without your constant encouragement. You never give up on me. You’re always there.
Thank you to the love of my life, Marisa Chattman, for being a perfect partner and
thesis editor.
Thank you to my sister, Laura, for being my closest family and a constant supporter.
To my friend Jason Costigan, thank you for motivating me to finish my project by
finishing your master’s degree program first!
6. vi
Lastly, special thanks to Carlos, Pedro, and Bamboo, the furry creatures who gave
me constant love and attention through the many late nights spent at my desk and on my
couch reading and writing.
7. vii
Table of Contents
Acknowledgments............................................................................................................... v
List of Tables ...................................................................................................................... x
List of Figures.................................................................................................................... xi
I. Introduction and Background....................................................................................... 12
Aquaculture of microalgae to produce omega-3 fatty acids ................................. 12
Overfishing and Omega-3 Supply ........................................................................ 13
Waste in the Life Sciences.................................................................................... 14
Using Waste to Grow a Product............................................................................ 17
The Biology of Microalgae....................................................................... 18
Health benefits of omega-3 fatty acids ..................................................... 19
Omega-3 Fatty Acid Production............................................................... 20
Omega-3 Fatty Acid Production in Microalgae........................................ 21
Industrial Processing of Omega-3 Fatty Acids in Microalgae.................. 22
Harvesting Microalgae.............................................................................. 26
Extraction and Purification of Omega-3 Fatty Acids from Microalgal
Biomass..................................................................................................... 27
Managing Waste for a Carbon Dioxide Source.................................................... 28
Biological Waste....................................................................................... 29
Waste Management Technologies........................................................................ 33
Incineration ............................................................................................... 34
Plasma Gasification .................................................................................. 35
8. viii
II. Methods....................................................................................................................... 38
Selecting a disposal technology............................................................................ 39
Life Cycle Assessment.......................................................................................... 39
Life Cycle Assessment Goal..................................................................... 39
Functional Unit ......................................................................................... 41
System Boundaries.................................................................................... 41
Determining LCIA.................................................................................... 42
Estimating volume of waste needed to sustain microalgae culturing system....... 44
Creating a microalgae culturing system................................................................ 44
Selecting the species of microalgae...................................................................... 47
III. Results........................................................................................................................ 49
Biohazardous Waste Composition........................................................................ 49
Life cycle assessment of waste disposal technologies.......................................... 49
Estimation of carbon dioxide production from plasma gasification..................... 53
Algae Species Selection and Estimation of Omega-3 Production........................ 54
IV. Discussion and Conclusions ...................................................................................... 61
Description of the biological waste stream........................................................... 61
Waste Disposal Technology Selection.................................................................. 65
A Stable Source of Carbon Dioxide...................................................................... 69
Farming Nannochloropsis oculata ........................................................................ 71
Technology Innovations for Tomorrow................................................................ 76
Concluding Remarks............................................................................................. 80
10. x
List of Tables
Table 1. Advantages and limitations of open ponds and photobioreactors.............. 18
Table 2. Summary of PUFA enrichment processes….…...……………………..… 22
Table 3. Classification of Infectious Microorganisms by Risk Group…....……..... 26
Table 4. Estimated Composition of Synthetic Gases from Plasma Gasification of
Biological Waste……………………………………………………..…...48
11. xi
List of Figures
Figure 1. Examples of a bioprocess production chain in a microalgal biorefinery.
Apart from omega-3 fatty acids, the product portfolio includes biodiesel
and protein rich animal feed from the remaining
biomass……………………………………………………………...……. 16
Figure 2. Process diagram showing necessary steps for the conversion of waste to
omega-3 fatty acids……………………………………………………..... 32
Figure 3. System boundary of the comparative LCA study………..………...…….. 36
Figure 4. Racetrack design for a micro-algae pond………………………...………. 40
Figure 5. Small open ponds in Southern California used to conduct experiments to
determine optimal conditions for farming Nannochloropsis Oculata for
Omega-3 fatty acids……………...…………………………….....….…… 50
Figure 6. Picture of a “rotifer” micro-organism under the microscope (50X)…...… 52
Figure 7. Images of the inside of biological waste containers showing various
plastic and paper waste materials…………………………...…………..... 58
12. 12
Chapter I
Introduction and Background
The expansion of human activities throughout the world has produced countless
innovations along with a long list of issues that negatively impact the environment and
ultimately human health and well-being. The human drive toward discovering better
technologies allows for the improvement of the quality of life but also for the mitigation
of the harmful effects that growing industries have on the environment locally, regionally
and globally. Measureable environmental impacts include the generation of greenhouse
gases, species endangerment and extinction, and the use of valuable resources such as
arable land and clean water. Various data collection programs and software innovations
allow for a much more comprehensive and detailed ability to measure environmental
impacts from industrial activities. The biotechnology industry thrives on innovation
however in the life sciences there are many activities that can be managed differently to
decrease the negative environmental impacts while achieving the same or better results.
Aquaculture of microalgae to produce omega-3 fatty acids
The industrial applications involving the use of microalgae have rapidly grown
with the expansion of new technologies. A significant push to use more biologically
based tools has been fueled by the rise in environmental issues, such as the abuse of
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natural resources and global warming. Applications involving microalgae include
(Subashchandrabosea, Ramakrishnan, Megharaj, Venkateswarlu, & Naidu, 2013):
• use as a biofuel,
• use as a product for human nutrition,
• animal or aquaculture feed,
• creation of biochar for use as a biofertilizer,
• to create recombinant proteins that may be used the nutraceuticals, cosmetics, food
and feed industries, and
• as a source of polyunsaturated fatty acids (PUFAs).
Potential environmental benefits that can be harnessed during the algae producing activities
include: carbon sequestration and wastewater processing.
Overfishing and Omega-3 Supply
Commercial fishing has long been an important source of various materials
including protein, vitamins A and D, minerals, beneficial amino acids and long-chain
omega-3 fatty acids (Demars, 2012). Omega-3 fatty acids are not produced by the human
body but are essential for metabolism and must be consumed as part of the diet. They are
a popular supplement that is in high demand for its eicosapentaenoic acid (EPA) which
has been linked to numerous health benefits.
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The high demand for this supplement has been shown to have a damaging impact
on the New England coastal ecosystem and food chain because species such as alewife,
Atlantic herring, and Atlantic menhaden are harvested in massive quantities. These
species play a vital role at the bottom of the food chain as a food source and as algae
eaters (Pew Environmental Group, 2007).
As the demand for supplements increases with our growing populations the need
for a sustainable source of omega-3 fatty acid oils becomes increasingly important if we
are to maintain a healthy ocean ecosystem. Microalgae farming is a source for omega-3
fatty acids that has great potential for large scale production.
Waste in the Life Sciences
Research and development of therapeutic solutions involves the use of
considerable resources and generates an equally significant amount of waste. Typical Life
Science facilities are involved in research with animals and laboratory scale chemical and
biological activities. There are also various administrative departments and common use
areas, such as cafeterias and office space, where paper, food, and various other related
wastes are generated. The efficient management of this material can become a difficult
task. A person must navigate through a sea of regulations, disposal and treatment options,
new and existing technologies, and vendors to determine the best options for minimizing
cost, maintaining or increasing operational efficiencies and minimizing the company’s
environmental footprint.
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One of the common waste streams generated at a Life Sciences facility is
biohazardous waste. Biohazardous waste describes waste materials that are a biological
hazard to living organisms. It includes medical waste, which consists of infectious or
potentially infectious waste to humans, as well as plant and animal research wastes that
are potentially dangerous to those organisms, and genetically modified organisms that
may pose a threat to human, animal or environmental health (Mecklem & Neumann,
2003). According to the World Health Organization, biohazardous waste is the waste type
suspected to contain pathogens (bacteria, viruses, parasites, or fungi) in sufficient
concentration or quantity to cause disease in susceptible hosts (Prüss, Giroult, &
Rushbrook, 1999). These waste streams are believed to be high in organic content,
however, the composition of biotechnology biological waste has not been identified.
Regulatory oversight requires biohazardous wastes be destroyed either by thermal
decomposition or chemical treatment. Today, approximately 80% of the medical and
biohazardous waste in the US is disposed via offsite treatment (Forsman, 2013). This
waste is either transported to a medical waste incinerator for destruction or to an
autoclave to render the waste non-infectious. The ash from incineration and the solid
waste that is autoclaved is then landfilled. Currently, a significant portion of these wastes
are incinerated. This generates greenhouse gasses, primarily carbon dioxide, and renders
potentially energy rich wastes unrecoverable. Incineration activities also generate gas
emissions that contain various amounts of acid gas, carbon monoxide, lead, cadmium,
mercury, particulate matter, chlorinated dibenzodioxin, chlorinated dibenzofuran, NOx (a
generic term for mono-nitrogen oxides NO and NO2), and sulfur dioxide (SO2); all of
16. 16
which are deemed hazardous air pollutants by the USEPA (United States Environmental
Protection Agency, n.d.).
Waste incineration is a relevant contributor of emissions that contribute to global
warming potential (GWP). These emissions include carbon dioxide, dinitrogen oxide, and
methane. Human activities have increased the concentration of greenhouse gasses (GHG)
in the atmosphere. This is expected to warm the Earth’s surface leading to climate
change. Efforts to slow the potential for climate change include measures to reduce the
emissions of CO2, reduce emissions of non-CO2 GHG’s and to promote carbon
sequestration.
A popular incineration option is to use a waste- to -energy facility for disposal.
This option uses plasma for the destruction of burnable wastes. Even though a significant
amount of carbon dioxide and ash are still generated, the use of plasma gasification
technology to dispose of wastes is becoming a more attractive option. The high heat of
plasma disintegrates materials to very basic components that can be utilized in the
production of fuels and other commercially viable products. These components are
syngas (a mixture of CO, H2, and CO2,) and slag (a mixture of metal oxides) (Kuo,
Wang, Tsai, & Wang, 2009). Commercial plasma gasification facilities in the US
generate energy from the heat released by plasma but they do not efficiently utilize the
gasification by-products.
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Using Waste to Grow a Product
Currently the option to gasify waste biological waste does not exist. Should this
option become available in the future, a biotechnology company could divert organic
waste for gasification which would minimize emissions of environmentally harmful
pollutants and generate syngas that can be used to create useful products. Instead of
releasing the carbon rich syngas into the atmosphere it can be diverted to a
biotechnological process that can consume greenhouse gases and produce materials that
benefit the environment. This disposal technology could also be a source of negative
emissions because there are options for generating energy during the process.
The use of carbon capture and storage technology avoids the emissions of CO2 at
the generation site. This method is considered at WTE facilities where syngas and heat
are used to generate electricity. With society looking for ways to eliminate GHG
emissions, this option has been shown to be an effective method (Zeman, 2010). The
capture of CO2 from the plasma gasification process can then be transported and stored
for future use.
The carbon rich gasses generated from plasma gasification could be sequestered
to a living system that generates useful products. The culturing of algae has been shown
to use CO2 to enhance plant and microbial growth (Kumar, Dasgupta, Nayak, Lindblad,
& Das, 2011). One such system is the use of aquaculture to grow algae for the production
of omega-3 fatty acids. Enhancing the growth of algae using collected CO2 can have a
substantial impact on decreasing GHG emissions while generating a useful product that
18. 18
successfully sequesters carbon that would otherwise be emitted to the atmosphere
(Adarme-Vega, et al., 2012). Furthermore innovative research can continue to enhance
the ability of algae to sequester CO2 and produce larger amounts of fatty acids. Various
methods to genetically engineer microalgae have been successful at optimizing
photosynthesis, generating higher yields of fatty acids and producing a greater amount of
biomass. Ultimately, a microalgae culturing system that utilizes the syngas from the
gasification process will generate a number of benefits including safe and compliant
disposal of biohazardous wastes, pollution reduction, carbon sequestration, reduced
demand on the fishing industry, and the generation of a health supplement in high
demand.
The Biology of Microalgae
Algae are primitive plants known as the oldest life-forms on earth due to their
lack of roots, stems, and leaves. They also have no sterile covering of cells around the
reproductive cells and have chlorophyll a as their primary photosynthetic pigment
(Brennan & Owende, 2010). Algae are simply evolved to efficiently convert energy
without robust cellular development, allowing them to adapt to changing environmental
conditions. Based on the International Code of Botanical Nomenclature, the phycologists
consider microalgae to be of both eukaryotic and prokaryotic (cyanobacteria) cell types
(Subashchandrabosea, Ramakrishnan, Megharaj, Venkateswarlu, & Naidu, 2013).
19. 19
Algae are either autotrophic, heterotrophic, or mixotrophic. Heterotrophs are non-
photosynthetic and require an external source of organic compounds and nutrients as an
energy source for survival. Autotrophs require only inorganic carbon (e.g., carbon
dioxide), salts, and a light energy source for growth, a process known as photosynthesis
(Brennan & Owende, 2010). Autotrophic algae utilize photosynthesis to convert solar
radiation and carbon dioxide into adenosine triphosphate (ATP) and oxygen which is
used in respiration to produce energy supporting growth and propagation. Mixotrophic
algae have the ability to generate energy from photosynthesis and through acquisition of
exogenous organic nutrients (Brennan & Owende, 2010). Due to the ability of
autotrophic algae to fix atmospheric carbon dioxide during photosynthesis, a process
utilizing this type of algae is optimal for the purposes of this project.
Health benefits of omega-3 fatty acids
Omega-3 fatty acids are polyunsaturated fatty acids (PUFAs) which provide
significant health benefits to humans. The eicosapentaenoic acid (EPA) and
docosahexaenoic acid (DHA) have been found to be the most important fatty acids to
reduce cardiac diseases such as arrhythmia, stroke and high blood pressure as well as
offering beneficial effects to depression, rheumatoid arthritis and asthma (Tong, et al.,
2012) (Robinson & Stone, 2006) (Lee, O'Keefe, Lavie, & Harris, 2009) (Ross, Seguin, &
Sieswerda, 2007). In addition to the cardiovascular benefits, there is evidence indicating
omega-3 fatty acids enhance brain and nervous system function (Simopoulos & Bazan,
20. 20
Omega-3 Fatty Acids, the Brain and Retina, 2009). When used as immunomodulators,
benefits have been observed during treatment of inflammatory diseases such as cystic
fibrosis, asthma, lupus, Crohn’s disease, ulcerative colitis, psoriasis, and rheumatoid
arthritis (Stenson, et al., 1992) (Simopoulos, 2002). These health promoting effects have
increased demand for microalgae in the pharmaceutical and nutraceutical industries.
Microalgal PUFAs and extracts are used in a variety of products including: infant
formulae, face and skin care applicants, anti-aging cream, sun protection cream, and anti-
irritant in peeler treatments (Spolaore, Joannis-Cassan, Duran, & Isambert, 2006).
Omega-3 Fatty Acid Production
Fatty fish, such as salmon, mullet and mackerel, are the primary source for these
fatty acids but utilizing fish as a source has numerous unattractive side effects. Over
fished stocks negatively impact the vital marine food chain (Buchsbaum, Pederson, &
Robinson, 2005). The use of fish also renders the supplements unsuitable for vegetarians
and lends to unattractive odors. Lastly, fish have also long been known to bio-accumulate
chemicals, such as mercury, which are harmful to consumers (Adarme-Vega, et al.,
2012). The benefits of consuming fish derived omega-3 fatty acids are well documented;
however, the negative effects indicate that alternate sources for these supplements should
be exploited (United States Food and Drug Administration).
Bacteria, fungi, plants and microalgae are being explored for commercial
production of omega-3 fatty acids. Fungi require an organic carbon source and have long
21. 21
growth cycles while plants require arable land, have long growth cycles, and must be
genetically engineered to induce the production of PUFAs (Barclay, Meager, & Abril,
1994) (Ursin, 2003). Alternatively, microalgae have faster, natural grown cycles that can
be controlled under a variety of conditions. The growth of microalgae does not have to
depend on seasonal variations due to the technologies available that allow for year round
production. Additionally, microalgae fix carbon dioxide and can be grown on non-arable
land reinforcing its positive environmental impact (Brennan & Owende, 2010). A
comparison shown in Appendix 1 indicates microalgae generate higher concentrations of
PUFAs than other sources.
Omega-3 Fatty Acid Production in Microalgae
The high levels of oils, lipids, and fatty acids generated in marine microalgae are
closely linked to the algal growth stages and environmental conditions. Under poor
environmental conditions or during cell division, omega-3 fatty acids are accumulated
due to their high energy content and to assist with critical cellular functions (Cohen,
Khozin-Goldberg, Adlerstein, & Bigogno, 2000). This accumulation is initiated for
survival in response to growth limiting stresses such as UV radiation, temperature, and
nutrient deprivation (Adarme-Vega, et al., 2012). The production of omega-3 fatty acids
can be controlled by modifying growth conditions. For example, Pavlova lutheri
increased its relative EPA content from 20.3 to 30.3 % when the temperature was
decreased to 15°C (Tatsuzawa & Takizawa, 1995).
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Another promising approach to increasing the production of omega-3 fatty acids
has been the use of genetic engineering (Schuhmann, Lim, & Schenk, 2012). More
research is needed to gain a better understanding of the mechanisms involved in the fatty
acid biosynthetic pathways in microalgae; however, genes have been identified for
encoding key enzymes in Ostreococcus tauri, Thalassiosira pseudonana, Phaeodactylum
tricornutum, and Chlamydomonas reinhardtii (Adarme-Vega, et al., 2012). Additional
gene-based actions for PUFA degradation inhibition remain exciting options as mutations
in one or more saturates may result in less efficient β-oxidation of PUFA and a higher
percentage of these fatty acids (Adarme-Vega, et al., 2012).
Industrial Processing of Omega-3 Fatty Acids in Microalgae
There is great potential in utilizing autotrophic microalgae for the production of
numerous materials, particularly omega-3 fatty acids, on a large scale. Figure 1 shows the
steps necessary for omega-3 fatty acid production in a microalgae biorefinery. Various
industries invest in microalgae production for the generation of nutraceutical and
pharmaceutical ingredients, biofuels, and protein-rich biomass (Adarme-Vega, et al.,
2012). The large scale production of autotrophic microalgae can be engineered using a
variety of differing technologies that include using open ponds or closed photobioreactors.
The use of hybrid facilities that combine both systems has also been explored with success
(Brennan & Owende, 2010).
23. 23
Figure 1. Examples of a bioprocess production chain in a microalgal biorefinery. Apart
from omega-3 fatty acids, the product portfolio includes biodiesel and protein rich animal
feed from the remaining biomass (Adarme-Vega, et al., 2012).
Cultivation in open pond systems has been used since the 1950’s and can be
installed into natural waters and artificial ponds or containers. Open pond systems are
simpler and cheaper to manage than photobioreactor systems but are found to be less
efficient at producing biomass for a number of reasons (Table 1). Open pond systems are
more susceptible to contamination and pollution, may limit light exposure, can
Microalgae
Culturing
Harvesting
Lipid Extraction
Output
Ʊ-3
Biodiesel
Biomass
Raceway
Photobioreactor
Open Pond
Solvent
Supercritical fluid extraction
Winterization
Distillation
Transesterification
Filtration
Flocculation
Centrifugation
24. 24
experience carbon dioxide deficiencies, and experience evaporative loss (Adarme-Vega,
et al., 2012). Also, poor mixing results in poor carbon dioxide transfer rates causing low
biomass productivity (Ugwu, Aoyagi, & Uchiyama, 2008).
Table 1. Advantages and limitations of open ponds and photobioreactors (Brennan &
Owende, 2010)
Production System Advantages Limitations
Raceway Pond
Relatively cheap Poor biomass productivity
Easy to clean Large area of land required
Utilizes non-agricultural land Limited to a few strains of algae
Low energy inputs Poor mixing, light and CO2 utilization
Easy Maintenance Cultures are easily contaminated
Tubular photobioreactor
Large illumination surface area Some degree of wall growth
Suitable for outdoor cultures Fouling
Relatively cheap Requires large land space
Good biomass productivities Gradients of pH, dissolved oxygen and CO2 along
the tubes
Flat Plate Photobioreactor
High biomass productivities Difficult to scale-up
Easy to sterilize Difficult temperature control
Low oxygen build-up Small degree of hydrodynamic stress
Readily tempered Some degree of wall growth
Good light path
Large illumination surface area
Suitable for outdoor cultures
Column Photobioreactor
Compact Small illumination area
High mass transfer Expensive compared to open ponds
Low energy consumption Shear stress
Good mixing with low shear
stress
Sophisticated construction
Easy to sterilize
Reduced photoinhibition and
photo-oxidation
Closed photobioreactor systems are known to generate high yields of algal
biomass with greater efficiency. The closed system allows for better contamination
control and permits the cultivation of microalgae for extended periods of time (Adarme-
Vega, et al., 2012). These systems currently exist as tubular, flat plate and column
25. 25
photobioreactors. These straight glass or plastic tubular arrays capture sunlight and
recirculate algae cultures either with a mechanical pump or airlift system. Column
photobioreactors are arguably the most attractive technology for microalgae production
as they allow for more efficient mixing, offer the highest volumetric mass transfer rates
and the best conditions for cultivation (Eriksen, 2008). They are also low cost, compact
and easy to operate (Adarme-Vega, et al., 2012).
The increased amount of research into the closed bioreactor systems is very likely
due to the greater degree of control that closed systems have over the open systems. This
allows for higher biomass production rates and therefore greater generation of desirable
algae products, such as omega-3 fatty acids (Appendix 2).
Optimizing the photosynthesis of microalgae will allow for a greater yield in algal
oils and biomass. Various methods for enhancing photosynthesis using genetic
engineering have been proposed. One method involves genetically engineering algal
species to produce photosynthetic pigments that would allow for a greater amount of the
light spectrum to be absorbed for energy production. Typical biological systems harness
radiation in the wavelength range of 400-700 nm. By engineering the pigments
Chlorophyll f (706 nm), Chlorophyll d (710 nm), and bacteriochlorophyll (700-1000 nm)
into microalgae a greater range of radiation will be available for photosynthesis (Chew &
Bryant, 2007) (Chen, et al., 2010).
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Harvesting Microalgae
There are various harvesting technologies available for microalgae producers.
Selecting the proper technology is important to accumulating higher levels of biomass
and is dependent on the species of microalgae being cultivated. The processes available
include flocculation, filtration, flotation, and centrifugal sedimentation and involve the
bulk harvesting of the microalgae followed by thickening of the accumulated slurry
(Adarme-Vega, et al., 2012). The selection of a harvesting technology should attempt to
capture the following features (Uduman, Qi, Danquah, Forde, & Hoadley, 2010):
• Low energy consumption,
• Complete recycling of water and nutrients,
• No addition of harmful chemicals/materials, and
• A compact unit of small-foot print.
Flocculation is a step taken prior to the algae harvesting that is necessary to
concentrate the algae. Algae, which carry a negative charge, do not aggregate naturally in
suspension and by adding flocculants the charge repulsion is overcome. Flocculants are
multivalent cations and cationic polymers that neutralize this charge enhancing the ability
of the algae to aggregate (Brennan & Owende, 2010). Several flocculation harvesting
methods have been tested and shown to be efficient, however there is a lack of
information and comparative studies for micro-algae (Uduman, Qi, Danquah, Forde, &
Hoadley, 2010). Centrifugation is a rapid and energy intensive harvesting technology
(Uduman, Qi, Danquah, Forde, & Hoadley, 2010). It is considered an efficient and
27. 27
reliable method but higher energy and maintenance costs persist. Biomass filtration may
be used for larger (>70µm) or smaller (<30µm) microalgae. Larger microalgae may be
harvested by conventional filtration, which operates under pressure or suction. Membrane
microfiltration and ultra-filtration methods used for smaller microalgae have been found
to be more cost effective than centrifugation when processing low volumes (<2m3
)
(Uduman, Qi, Danquah, Forde, & Hoadley, 2010). The cost of membrane replacement
and pumping required for large scale operations (>20m3
) indicate that centrifugation may
be a more cost effective method for algal biomass harvesting (Uduman, Qi, Danquah,
Forde, & Hoadley, 2010).
Extraction and Purification of Omega-3 Fatty Acids from Microalgal Biomass
Prior to lipid extraction the harvested microalgal biomass must be dewatered and
dried (Adarme-Vega, et al., 2012). Methods used include sun drying, low-pressure shelf
drying, spray drying, drum drying, fluidized bed drying, freeze drying and Refractance
Window technology drying (Brennan & Owende, 2010). After dehydrating the biomass a
solvent based extraction method is used. The solvent used varies depending on the scale
of the extraction. Smaller operations typically use mixtures of methanol and chloroform
for lysing cells and lipid extraction, while larger scale extractions typically use hexane
(Adarme-Vega, et al., 2012). This is followed by separation of the unsaturated fatty acids
from the total lipids by fractional distillation or winterization. Additional technologies
28. 28
(Table 2) are used to further enrich and purify the PUFA, particularly when used to
produce products intended for human consumption (Adarme-Vega, et al., 2012).
Table 2. Summary of PUFA enrichment processes (Adarme-Vega, et al., 2012)
Method Procedure
Molecular distillation (Fractional distillation) Purification of fatty acid esters in a vacuum
system based on the different boiling points of
different fatty acids.
Molecular sieves Separation via membrane permeability and
selectivity.
PUFA transformations Esterification of PUFA and free fatty acids to
produce esters (ethyl-, glyceryl-, sugar-, other).
Inter-esterification to enrich lowly unsaturated
fatty acids with PUFA.
Super Critical Fluid Extraction Optimization of lipid solubility and fractionation
in supercritical CO2.
Urea Complexation Solubilization of fatty acids, adding urea and
ethanol to saturation point exposing it to heat.
Recovery of product by filtration.
Winterization Temperature reduction to render more saturated
fats insoluble.
Managing Waste for a Carbon Dioxide Source
The first step of waste management is to complete waste identifications. This
crucial first step is necessary to determine the components contained in waste and
subsequently, how those components can be managed and disposed. This process must be
in compliance with various regulatory entities and utilize the best demonstrated available
technology to decrease the environmental impact of disposal. A very broad way of
initially segregating waste types is to categorize by radioactive, chemical, biological, or
non-hazardous characteristics.
29. 29
Biological Waste
Biological waste is known by numerous terms. It is common to hear it referred to
as medical waste, hazardous medical waste, healthcare waste, and biohazardous waste.
For the purposes of this project we will use the term “biological waste” which includes
wastes that are infectious (samples or cultures known to be infectious in healthy human
adults), potentially infectious (uncharacterized human or non-human primate tissue or
body fluid samples), and non-infectious (samples known to not be infectious in healthy
human adults). The management of biological wastes in the life sciences typically results
in offsite disposal of such wastes via incineration. There an estimated 33 medical waste
incinerators in the US, all which utilize fossil fuels to power their destruction activities
(Hambrick, 2013). State authorities usually regulate biological waste. The EPA has
released a guidance document to assist states in the implementation of their biological
waste regulations, though it has not been updated since its original publication in 1992.
The Center for Disease Control and the National Institutes of Health have guidelines for
the management of a biological safety program which includes the management of
biological wastes. The state of Massachusetts defines biological waste as (Department of
Public Health, 2007):
Waste that because of its characteristics may cause, or significantly contribute to,
an increase in mortality or an increase in serious irreversible or incapacitating
reversible illness; or pose a substantial present potential hazard to human health or
the environment when improperly treated, stored, transported, disposed of, or
otherwise managed.
30. 30
Massachusetts also identifies and defines the following types of waste as biological waste
(Department of Public Health, 2007):
(1) Blood and Blood Products. Discarded bulk human blood and blood products in free
draining, liquid state; body fluids contaminated with visible blood; and materials
saturated/dripping with blood. Blood Products shall not include; feminine hygiene
products.
(2) Pathological Waste. Human anatomical parts, organs, tissues and body fluids
removed and discarded during surgery, autopsy, or other medical or diagnostic
procedures; specimens of body fluids and their containers; and discarded material
saturated with body fluids other than urine. Pathological waste shall not include:
Teeth and contiguous structures of bone without visible tissue, nasal secretions,
sweat, sputum, vomit, urine, or fecal materials that do not contain visible blood or
involve confirmed diagnosis of infectious disease.
(3) Cultures and Stocks of Infectious Agents and Associated Biologicals. All discarded
cultures and stocks of infectious agents and associated biologicals, including
culture dishes and devices used to transfer, inoculate, and mix cultures, as well as
discarded live and attenuated vaccines intended for human use, that are generated
in:
(a) Laboratories involved in basic and applied research;
(b) Laboratories intended for educational instruction; or
(c) Clinical laboratories
31. 31
(4) Contaminated Animal Waste. Contaminated carcasses, body parts, body fluids,
blood or bedding from animals known to be:
(a) Infected with agents of the following specific zoonotic diseases that are
reportable to the Massachusetts Department of Agricultural Resources, Bureau
of Animal Health pursuant to 105 CMR 300.140: African swine fever, Anthrax,
Avian influenza – H5 and H7 strains and any highly pathogenic strain, Bovine
spongiform encephalopathy (BSE), Brucellosis, Chronic wasting disease of
cervids, Foot and mouth disease, Glanders, Exotic Newcastle disease, Plague
(Yersinia pestis), Q Fever (Coxiella burnetti), Scrapie, Tuberculosis, Tularemia
(Francisella tularensis); or
(b) Infected with diseases designated by the State Epidemiologist and the State
Public Health Veterinarian as presenting a risk to human health; or
(c) Inoculated with infectious agents for purposes including, but not limited to, the
production of biologicals or pharmaceutical testing.
(5) Sharps. Discarded medical articles that may cause puncture or cuts, including, but
not limited to, all needles, syringes, lancets, pen needles, Pasteur pipettes, broken
medical glassware/plasticware, scalpel blades, suture needles, dental wires, and
disposable razors used in connection with a medical procedure.
(6) Biotechnology By-product Effluents. Any discarded preparations, liquids, cultures,
contaminated solutions made from microorganisms and their products including
genetically altered living microorganisms and their products.
32. 32
The last step in characterizing medical waste is to evaluate the level of risk posed
by the known biological agent in the waste materials. The NIH and WHO ranks all
biological agents into risk groups (Table 3).
Table 3. Classification of Infectious Microorganisms by Risk Group
Risk Group
Classification
NIH Guidelines for Research involving
Recombinant DNA Molecules 20022
World Health Organization Laboratory Biosafety
Manual 3rd Edition 20041
Risk Group 1 Agents not associated with disease in
healthy adult humans.
(No or low individual and community risk) A
microorganism unlikely to cause human or animal
disease.
Risk Group 2 Agents associated with human disease that
is rarely serious and for which preventive or
therapeutic interventions are often available.
(Moderate individual risk; low community risk) A
pathogen that can cause human or animal disease
but is unlikely to be a serious hazard to laboratory
workers, the community, livestock or the
environment. Laboratory exposures may cause
serious infection, but effective treatment and
preventive measures are available and the risk of
spread of infection is limited.
Risk Group 3 Agents associated with serious or lethal
human disease for which preventive or
therapeutic interventions may be available
(high individual risk but low community
risk).
(High individual risk; low community risk) A
pathogen that usually causes serious human or
animal disease but does not ordinarily spread from
one infected individual to another. Effective
treatment and preventive measures are available.
Risk Group 4 Agents likely to cause serious or lethal
human disease for which preventive or
therapeutic interventions are not usually
available (high individual risk and high
community risk).
(High individual and community risk) A pathogen
that usually causes serious human or animal disease
and can be readily transmitted from one individual
to another, directly or indirectly. Effective treatment
and preventive measures are not usually available.
1. World Health Organization. Laboratory biosafety manual. 3rd ed. Geneva; 2004.
2. The National Institutes of Health (US), Office of Biotechnology Activities. NIH guidelines for research involving
recombinant DNA molecules. Bethesda; 2002, April.
All wastes determined to contain Risk Group 2 – 4 materials must be disinfected
to render the materials non-infectious or non-biohazardous. Movements to have validated
33. 33
procedures for the inactivation of biological agents are growing, as seen in current
agreements such as the CEN Workshop Agreement (CWA) 158793. Disinfection
typically occurs via thermal steam and pressure treatment (autoclave), chemical
treatment, or incineration. Some disinfection activities take place at the site of the waste
generation but much of the waste is shipped to disposal facilities for incineration.
Incineration facilities generate gas emissions that contain various amounts of acid gas,
carbon monoxide, lead, cadmium, mercury, particulate matter, chlorinated dibenzodioxin,
chlorinated dibenzofuran, NOx, and sulfur dioxide (SO2) (Vergara & Tchobanoglous,
2012). These emissions products are common during incineration activities that involve
the use of fossil fuels and are tracked and controlled by the US EPA.
Waste Management Technologies
There are a number of different ways to manage waste after collection. Various
technologies can be harnessed to transform waste into useful products. These methods
can reduce the amount of waste requiring disposal and can recover resources and energy.
One method uses biological systems to convert the organic fraction of waste (biogenic
wastes) into energy and soil amendments. Soil amendments are known to be material
such as lime, gypsum, sawdust, compost, animal manures, crop residue or synthetic soil
conditioners that are worked into the soil or applied on the surface to enhance plant
growth. Amendments may contain important fertilizer elements but the term commonly
refers to added materials other than those used primarily as fertilizers. The degradation of
34. 34
organic wastes occurs naturally and a thorough understanding of this microbiological
process can allow for the extraction of useful resources and the diversion of materials that
may be harmful to human and environmental health. A second method utilizes non-
biological processes to recover materials or energy. Also known as non-biogenic waste
transformation, this method includes incineration, pyrolysis, plasma gasification, and
recycling.
Incineration
Incineration is the thermal treatment of organic wastes using carbon-based fuels
that results in the generation of ash, air emissions (NOX, CO, CO2, SO2, PM, dioxins,
furans, and others), heat, and energy (Vergara & Tchobanoglous, 2012). This process
reduces the volume of solid waste by 80-85% and allows for energy recovery when the
proper technologies are in place (Quina, Bordado, & Quinta-Ferreira, 2008). However,
the ash and air pollutants emitted represent an environmental burden. Modern
incinerators have pollution controls that can lower the pollutant emissions to meet
regulatory standards. Cyclones, electrostatic precipitators, and fabric filters remove
particulate matter from the flue gas; scrubbers remove acid gases; catalytic reduction and
temperature control minimize NOX emissions; and activated carbon removes dioxins,
furans, and heavy metals from the flue gas (Quina, Bordado, & Quinta-Ferreira, 2008).
The ash consists of fly ash and bottom ash. The fly ash constitutes more of a health
hazard than does the bottom ash because the fly ash often contains high concentrations of
35. 35
heavy metals such as lead, cadmium, copper and zinc as well as small amounts of dioxins
and furans (Chan & Kirk, 1999).
Plasma Gasification
Plasma gasification technology is not new but it is emerging as a disposal option
that can provide solutions to numerous environmental, social, and economic issues. A
growing world population means increased demands for more energy and resources.
Landfills continue to be dead end dumping grounds for solid waste. The use of plasma
gasification can alleviate the burden placed on landfills since such wastes can be utilized
as fuel. The gasification process can utilize a variety of carbon based materials such as
garbage, plant material, hazardous, and biological wastes.
Plasma is known as the 4th
state of matter after solid, liquid and gas. It is created
when gases are superheated allowing them to become electrically conductive, such as in
lightening or on the surface of the sun (Prüss, Giroult, & Rushbrook, 1999). Plasma
technology involves passing electrical current through a gas generating heat due to
electrical resistivity. This process generates plasma, an ionized gas stream that has a
liquid-like viscosity and conductivity that can approach those of metals (Auciello &
Flamm, 1989). The temperatures of a plasma arc can reach 10,000 °F creating a system
capable of destroying any substance found on Earth with the exception of radioactive
materials.
36. 36
There are various applications that use plasma technologies including (Auciello &
Flamm, 1989):
a) Coating techniques, such as plasma spraying, wire arc spraying and thermal
plasma chemical vapor deposition (TPCVD);
b) Synthesis of fine powders, in the nanometer size range;
c) Metallurgy, including clean melting and re-melting applications in large furnaces;
d) Extractive metallurgy including smelting operations;
e) Destruction and treatment of hazardous and non-hazardous waste materials.
The use of plasma gasification for waste disposal is very attractive due to its
ability to destroy the solid matter and transform it into basic components: syngas and
slag. Slag is a glass-like solid material composed of the inorganic elements present in
plasma treated wastes. The composition of slag changes depending on the nature of the
treated waste however it is usually composed of metals and various oxides such as
aluminum oxide (Al2O3), calcium oxide (CaO), silicon oxide (SiO2), iron oxide (Fe2O3),
sodium oxide (Na2O) and magnesium oxide (MgO) (Demars, 2012) (Byun, et al., 2010).
The volumetric reduction of waste to slag from plasma gasification is up to 99%, a
significantly greater proportion than a conventional waste incinerator utilizing a fuel
burning system which reduces the volume of waste by 90% (Bie, Li, & Wang, 2007).
Another benefit of generating slag containing heavy metals and other contaminants is that
the hazardous components are effectively immobilized thus keeping them from leaching
out into the environment (Bie, Li, & Wang, 2007).
37. 37
Syngas consists of carbon monoxide (CO), hydrogen gas (H2), and carbon dioxide
(CO2). Recent advances in plasma gasification technologies allow for the generation of a
much cleaner syngas allowing it to be used safely to produce fuels and other products.
The typical plasma gasification process (Appendix 3) utilizes a plasma gasifier,
the chamber where organic waste is fed to the plasma torches. In this gasifier the plasma
jets are located at the bottom where they generate sufficient heat for the gasification of
waste to occur. As the waste descends through the chamber it is converted to gas and
liquid slag. The gas generated is also known as syngas and consists of CO, H2, and small
amounts of CO2. The syngas is then passed through a secondary combustion chamber
where it is converted to CO2 and water.
38. 38
Chapter II
Methods
The primary objective of this project was to create a process to sequester carbon
rich gas emissions into algae cultivated with the intention of producing omega-3 fatty
acids in Southern California. This process combines microalgae production and
biohazardous waste disposal to create a more sustainable and productive system.
To build an efficient system for converting biohazardous waste into omega-3 fatty
acids by utilizing plasma gasification and algae farming technologies the process shown
in Figure 2 was created.
Figure 2. Process diagram showing necessary steps for the conversion of waste to
omega-3 fatty acids.
• Collection
• Transportation
Biohazardous
Waste
CO2 Capture and
Storage
Plasma
Gasification
• Carbon
Sequestration
• Role of
Biotechnology
• Culturing &
Harvesting
Algae Farming
• Extraction
from algae
biomass
• Purification
Omega-3 Fatty
Acids
39. 39
Selecting a disposal technology
Biological waste disposal technologies have not experienced much change since
the EPA released its guidance document for biohazardous waste management to states in
1992. Current methods involve incineration, chemical disinfection and thermal and
pressure treatment. Plasma gasification is not used for the incineration of biological waste
however if used efficiently such a technology could be a valuable option for waste
generators.
Using life cycle assessments (LCAs) municipal incineration, plasma gasification
and autoclaving/landfilling were compared to measure their environmental impacts.
Life Cycle Assessment
Life Cycle Assessment Goal
The process known as life cycle assessment (LCA) is used to evaluate the GHG
emissions throughout the full product or service life cycle. The International Standards
Organization (ISO) has developed standards for conducting LCAs that can be applied to
industrial activities and associated GHG emissions, capture, and sequestration. LCA is a
methodology that provides certain principles and framework to analyze the
transformation processes and infrastructure required to produce the main products and
co-products for an energy production operation in order to estimate its environmental
impacts. The use of this technique for assessing environmental impacts involves: 1)
generating an inventory of linked energy and material inputs and environmental releases,
40. 40
2) Evaluating the possible environmental impacts associated with the inputs and releases,
and 3) Interpreting the results to support more informed decision making (Scientific
Applications International Corporation, 2006).
The LCA analysis of the environmental performance of a waste disposal system should
include emissions from the system being evaluated, emissions from other sources
indirectly linked with the system under evaluation, emissions from production processes
of electricity used in the system being evaluated, all emissions avoided, and emissions
from processes of recycling and benefits, or emissions avoided because of replaced virgin
production of materials by the recycling processes (Pikoń & Gaska, 2012). The
production of one material often involves production of byproducts or waste. When a
byproduct is used to replace another product from a different process, a portion of
environmental damage can be avoided. The values for the avoided damage can be
calculated using the LCA approach and are termed “displacement credits” (Pikoń &
Gaska, 2012). LCA has several sequential steps in which the goal and scope of the
project are defined, then a Life-Cycle Inventory (LCI) is performed. This LCI is used to
assess impacts using a set of environmental damage indicators. Results are compiled and
interpreted to compare environmental impacts of different projects in an objective way
(Bauman & Tillman, 2004). A LCIA measures the link between the process and its
potential environmental impacts. This should address ecological and human effects as
well as resource depletion (Scientific Applications International Corporation, 2006).
Using these systems we will measure the environmental damage mitigated by using the
alternative technology, plasma gasification.
41. 41
Functional Unit
The use of a functional unit in the LCA is necessary to compare two or more
products or services. The functional unit should describe the function of the services
being compared (Scientific Applications International Corporation, 2006). The LCA for
this project will compare the disposal of biohazardous waste by plasma gasification,
autoclave/landfill, and incineration. The functional unit for this study has been defined as:
“The disposal of 8129.3 Kg of biohazardous waste.”1
The use of the functional unit has allowed for the calculation the amount of
carbon rich gas that can be sequestered during the algae culturing process.
System Boundaries
The geographical boundaries of this study will be limited to Southern California.
The boundaries of the technical system are shown in Figure 3. Within the boundary the 3
options include cradle-to-grave analysis of the collection and disposal of waste and the
impact of gas capture. Options B and C allow for the direct comparison between existing
waste disposal processes while Option A is the proposed alternative process which was
used to demonstrate the impact of gas capture on the process LCA.
1
This unit was derived from disposal metrics of a medium sized (~300 employees and ~100,000
ft2
laboratory space) biotechnology company located in Cambridge, MA, throughout 2012.
42. 42
Determining LCIA
The results of an LCIA should show the relative differences in potential impacts
for each option shown in Figure 3 and will provide an estimation of health and
environmental effects of omega-3 fatty acid production using carbon from plasma treated
waste to farm algae.
Figure 3. System boundary of the comparative LCA study
Life-Cycle Inventories (LCI) for pollutant emissions from regular (business-as-
usual) operations were estimated using libraries of average pollution emissions waste
processing and disposal contained in the EcoInvent 2.2 database within the OpenLCA V.
1.4 software. Average values come from the inventories of several thousands of
operations which are recorded in these libraries. Then, a life cycle inventory was made
Option A
100% Plasma Gasification
Collection of BHW
Plasma Gasification
Gas capture via microalgae
culturing
Option B
100% Regular Incineration
Collection of BHW
Regular Incineration
Gas capture via microalgae
culturing
Option C
Landfill
Collection of BHW
Autoclave
Landfill
No gas capture
43. 43
using plasma gasification and municipal incineration as a source of carbon dioxide. Life-
cycle inventories come from all pollutant emissions registered in LCI libraries for each of
these components. The end result of this first part of the analysis is a set of life-cycle
pollutant emissions (midpoint indicators) per functional unit of waste and microalgae
omega-3.
The life-cycle emissions per functional unit were used to perform an end-point
environmental damage assessment using global settings with the ReCiPe Method to
estimate overall damages to human health, ecosystem diversity and resources cost from
each operation. ReCiPe is an assessment method for environmental impacts created in
2008 that integrates a comprehensive set of damage functions and calculation methods
into a structured non-software based methodology. This LCA methodology has open
source information and values that can be modified to function in a regional scale. The
use of the ReCiPe method with world normalization provides preliminary values of
comparison between production projects. The units for these endpoint indicators are
Disability Adjusted Life Years (DALYs) for Human Health, Species.Year for Ecosystem
Diversity and $2010 USD for Resources Cost of depleting resources for future
generations. In this way these units are easily transferable for other health and
environmental analyses that require information about environmental impacts of waste
disposal and omega-3 fatty acid production operations.
44. 44
Estimating volume of waste needed to sustain microalgae culturing system
It will be important to calculate the volume of synthetic gas generated as this will
be a factor in calculating the biomass production potential of the microalgae that will
sequester the CO2. Gas volume from the incineration process will be estimated by
creating 1 ton of a mix of biohazardous waste with the same percentage composition to
the one estimated for the company in the case study. This biohazardous waste will be
gasified using a bench plasma torch built by using regular welding electrodes attached to
a ceramic container. Parameters from a Westinghouse Plasma incinerator in a poor
oxygen atmosphere will be used to emulate conditions of a full size prototype. Samples
of the resulting synthetic gas will be collected and analyzed with a gas chromatographer.
All gases and compounds with a 0.1% by weight or more of the total weight of the
sample will be listed as the main components of the synthetic gas. This gas composition
will be reproduced in the lab and used in a bench gas turbine in a pure oxygen
atmosphere in order to determine the amount of carbon dioxide produced by the process.
We will determine total CO2 generated from the functional unit by using this information.
Creating a microalgae culturing system
The fact that algae are potential sources for various oils and supplements is well
known. However, to create a sustainable process that generates sufficient amounts of
algae, cultivation and harvesting must be designed in a very specific manner. Microalgae
production is enhanced using a source of CO2. Conventional electric power generation
45. 45
with fossil fuels is a common source as well as waste incineration activities that utilize
either fossil fuels or plasma for waste destruction. Carbon rich emissions, known as
syngas, are generated by plasma gasification of biological wastes. CO2 is captured from
post-combustion gases using a monoethanolamine (MEA) plant where flue gases and
solvent (30% MEA solution) are mixed. MEA reacts with and captures CO2 so that the
gases can be transported for use at a microalgae production facility. In order to efficiently
utilize the trapped gas, the gasification facility should be near or part of the facility that
will cultivate and process the algae for the production of omega-3 fatty acids to minimize
costs associated with gas capture activities and transportation. In order to release the CO2
the MEA is heated which liberates the trapped gas which can then be fed directly to
algae. The CO2 recovery efficiency is approximately 91.2% (Al-Juaied & Whitmore,
2009) (Gonzalez-Diaz, et al., 2010).
Prior to adding CO2, microalgae ponds are built with a racetrack design and a
depth of 0.4 m (Figure 4), covered with a plastic liner, filled with pre-treated saltwater
and supplied with a water mixing system. A water mixing system is necessary to
maintain microalgae cells in suspension, to prevent thermal stratification, provide
uniform sunlight absorption for all microalgae cells in the pond and to disperse nutrients
(Natural Resources Defense Council, 2009). Water is pre-treated before entering the
system in order to avoid the formation of parasitic bio-mass that might use this rich
nutrient medium to overwhelm useful algae.
46. 46
Figure 4. Racetrack design for a micro-algae pond.
Microalgae strains are isolated from water samples in nature and cultured in
laboratory conditions. The algae ponds are inoculated with this algae culture and
exposed to sunlight. The mixing system is activated after inoculation and carbon dioxide
is added to the saltwater in a gaseous form as the final step of water treatment.
Algae biomass is harvested daily by extracting 30 to 35 % of the water with
microalgae from the pond (1000 to 1200 m3
/Hectare*day). Saltwater restocking is
continuous to compensate for water losses during harvesting and daily evaporation
(Benemann & Oswalk, 1996). Fresh or brackish water is treated and mixed with
saltwater to compensate for increases in salt concentration due to daily evaporation
(Energy and Environmental Research Center, 2002).
47. 47
Production yields are highly dependent daily fluctuations in physical conditions
and potential parasite contamination. Biomass will be separated from water by using a
centrifuge and electroflocculation (water passes through electrodes and polarizes the cell
wall of algae which tends to agglomerate so it is easy to extract it).
Selecting the species of microalgae
Considerations must also be made for the species of algae utilized. The ideal
species of autotrophic algae will efficiently harness light and carbon enriched media.
Experiments were conducted to identify the algal species that would most efficiently
produce EPA. Small scale experimentation to determine optimal species and growth
conditions has shown that cold water algae is likely to be an ideal candidate for growth
under controlled conditions for the production of omega-3 fatty acids (Fang, Wei, Zhao-
Ling, & Fan, 2004). For that reason, water samples will be taken from the sea in close
proximity to the coasts of California and Baja California and reviewed under the
microscope. Algae species will be isolated and identified. Then their fat, protein and ash
content will be estimated. Algae with the highest lipid content will be cultured in a
laboratory and types of lipids will be characterized to determine the species with the
highest concentration of unsaturated fats, particularly omega-3 fatty acids with EPA.
The algae species with the highest omega-3 content will be cultured in a lab, its species
and/or family will be recorded if identified. However, if the algae species is a new strain
it will be catalogued and assigned a number, then a sample will be sent to a specialized
48. 48
phycology (algae science) research laboratory for further family identification using
DNA sequencing. A 5,000 –liter open pond will be inoculated with the selected species.
Operating conditions will be continuously recorded and production rates will be
estimated daily for at least 15 days. The most likely conditions that influence algae
biomass production are nutrient quality and quantity, carbon dioxide concentration in
water, solar irradiation, culture media pH, turbulence, salinity, and water temperature.
Variations in these factors are likely to affect algae lipid production differently depending
on the algae species being cultured. For that reason, the significance of the most relevant
operating parameters and practices will be determined and characterized in the
production of omega-3 fatty acids with EPA.
49. 49
Chapter III
Results
Biohazardous Waste Composition
A biotechnology research company that employs approximately 300 people and
that has approximately 100,000 ft2
of laboratory space generates an annual average of
1129 biohazardous waste containers for disposal. The maximum weight that is permitted
per container is 50 pounds (22.7 kilograms). The average weight of each biohazardous
waste container was determined to be 15.86 pounds (7.20 kilograms).
Appendix 4 shows the results from the sampling of biohazardous waste containers
from a biotechnology research facility.
The calculation of the total annual average biohazardous waste (Appendix 4) is
the Functional Unit for all further LCA activities. Average composition for waste in the
Functional Unit is maintained in all calculations.
Life cycle assessment of waste disposal technologies
Using LCA software waste disposal technologies were evaluated to determine the
LCIA for each disposal option: regular incineration, landfill and plasma gasification.
Environmental impacts’ estimations include the process of incinerating and disposing of
8129.3 Kg of biohazardous waste, it does not include transportation and “legacy”
50. 50
environmental impacts, therefore all environmental impacts for raw materials extraction,
supply activities, manufacturing, warehousing, distribution and use of these items are not
considered in this analysis because pre-waste damages should be assigned to the useful
life of the products. This analysis only considers the disposal phase for the product, there
is no recycling involved because that activity would involve unnecessary health risks for
the general population as biological waste materials might be a source of potential
contagions for waste processing workers. All scenarios will use the same assumptions
dealing only with safe disposal activities for biological waste, so they can be compared
objectively.
The Landfill Scenario requires neutralization of biological threats before sending
biological waste to the landfill. Potential biological contamination is treated using an
autoclave that uses pressured steam at temperatures above 100 °C to kill any potential
pathogens attached to biological waste. The autoclave cycle assumed for the LCA is:
• Start at room temperature and increase temperature from 25 °C to 100 °C
• Increase pressure relative to the atmosphere from 0 to 1.7kg/cm2 at 100 °C
• Maintain sterilization at 121 °C and 1.7kg/cm2 for 15 minutes
• Bring materials back to atmospheric pressure and drop temperature to 100 °C
• Reduce temperature further to 50 °C
These biologically neutral materials can be disposed in a landfill after the autoclave
treatment.
51. 51
Disposal of biological waste using plasma gasification includes the molecular
disintegration of waste and the generation of inert slag and syngas emissions. A bench
plasma gasification device using a comparable composition of biohazardous waste
(Appendix 4) is used to simulate real working conditions for a large-scale plasma
gasification system. Exhaust gases from plasma gasification are analyzed to determine
their composition and caloric content to estimate potential electricity production using a
combined cycle gas turbine coupled with a thermoelectric power plant. Calculations for
electricity production are in the range of 580 to 640 KWh per metric ton of biohazardous
waste (average production of 620 KWh per metric ton). Environmental impacts of
substituting energy from the regular electricity mix are not considered because only
overall direct emissions are used to estimate environmental impacts.
Life cycle inventory assessments for incineration (Appendix 5), autoclave plus
waste landfill (Appendix 6) and plasma gasification (Appendix 7) for the functional unit
of 8129.3 Kg of biological waste are processed into Endpoint Environmental Impacts by
using ReCiPe damage factors with a Hierarchist (H) approach with world normalization
that considers a 100 year horizon for damages as this is the operating practice for the
United Nations Framework for Climate Change (Appendix 8).
Endpoint damages for Human Health are expressed in Disability Adjusted Life
Years (DALYs) which indicate the sum of years of potential life lost due to premature
mortality and the years of productive life lost due to disability (ReCiPe, 2008). Endpoint
damages to ecosystem diversity are expressed in Species.years which is a way to measure
52. 52
extinction rate. There is approximately one extinction caused per million Species.years
(ReCiPe, 2008). The disposal of 8129.3 Kg of biological waste using incineration causes
approximately 0.083 DALYs. Health damages from using an autoclave and landfilling
for the same amount of waste is 0.031 DALYs. When using a plasma gasification process
0.001 DALYs are caused. This is a 62.6% and 98.7% reduction respectively when
comparing gasification to regular incineration and autoclaving/landfilling of biological
waste (Appendix 9). Ecosystem damages are reduced by 86% when using autoclave and
landfilling of biohazardous waste and by 98.6% when using plasma gasification
(Appendix 9).
Resource depletion costs are expressed in 2008 US Dollars per year that future
generations would need to spend for additional exploration, extraction and processing
costs for non-renewable materials and oil due to increased scarcity. Resource depletion
costs due to disposing of 8129.3 Kg of biological waste using regular incineration are
$3931, $5593 when using an autoclave and landfilling process and $1686 if the plasma
gasification process is used (Appendix 10).
Therefore, environmental damages for all categories are the lowest when plasma
gasification is used to dispose of biological waste. Environmental impacts for the other
processes show mixed results. The process of autoclave and landfilling is better than
regular incineration for Human Health and Ecosystem Damages, and worse in resource
depletion costs.
53. 53
Estimation of carbon dioxide production from plasma gasification
Comprehensive analysis of exhaust gases from the plasma gasification process
shows that effluent gases are composed mainly by carbon monoxide, water and carbon
dioxide as these 3 gases represent 89% of the total mass of plasma incineration exhaust
gases when processing biohazardous waste (Table 4).
Table 4. Estimated composition of synthetic gases from the plasma gasification of
biological waste.
Effluent gas Wt % Vol %
CO 45.10% 35.40%
H2O 23.95% 29.28%
CO2 20.95% 10.49%
N2 4.32% 3.40%
H2 1.67% 18.26%
CH4 0.90% 1.24%
C2H6 0.67% 0.50%
C4H10 0.66% 0.25%
C3H8 0.49% 0.24%
C2H4 0.31% 0.24%
H2S 0.14% 0.09%
By using the estimated composition of synthetic gas generation from plasma
gasification, stoichiometric reactions for adding pure oxygen in the combustion process,
and information of the combined cycle operation it was estimated that 8129.3 Kg of
biological waste will generate 6958 kg of carbon dioxide, 1610 Kg of water, 980 Kg of
54. 54
nitrogen oxides and 18.21 Kg of sulfur dioxide. This reaction requires the addition of
2656 Kg of pure oxygen in order to reduce nitrogen oxides formation.
Algae Species Selection and Estimation of Omega-3 Production
Algae species selection was made by reviewing lipid content for 50 cold water
species. After reviewing the lipid contents, the 10 species with the largest amount of
lipids were isolated and cultured in a laboratory. A comprehensive analysis to determine
the type of prevailing lipids was conducted for these 10 species and after a careful
examination, the 3 species with the highest concentration of omega-3 fatty acids were
selected (Appendix 11).
The algae species with the highest omega-3 content is Nannochloropsis oculata
with an average of 40% of EPA (20:5 n-3) which is a form of high-value omega-3. This
species is found in all oceans globally, so there is no risk of becoming an invasive species
if there is an accidental spill of this microalgae to the sea or coastal bodies of water. This
species has also shown high tolerance to chloride which is used to clean algae production
ponds in case there is biological contamination.
Numerous factors affect algae growth, such as pest contamination, temperature,
CO2 availability, solar irradiation, rain, and wind. Attempting to control these factors
result in elevated operating costs. The use of coastal waters and technologies helps
maintain optimal culture conditions allowing for increased production of microalgae and
their oils. For that reason, Nannochloropsis oculata was farmed in 24 small racetrack
55. 55
ponds of 1000 liters each (approximately 1/3,000 of a hectare of a large scale microalgae
farm) to test different concentrations of carbon dioxide, nutrients, fresh and saltwater,
water levels and chemical pest control parameters (Figure 5).
Figure 5. Small open ponds used to conduct experiments to determine optimal conditions
for farming Nannochloropsis oculata for omega-3 fatty acids.
Growth rates and omega-3 content of biomass were assessed daily as the outcome
variables. These information were used to derive lessons learned and recommendations to
enhance biomass growth. Some of the most important discoveries for enhancing
microalgae growth are:
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• Water temperatures should never go above 30 °C or below 5 °C. This is
important to be able to get meaningful amounts of lipids from algae. Any
temperature above 30 °C increases cell mortality and reduces biomass production.
Any temperature below 5 °C reduces algae metabolism to a minimum which
reduces reproduction rates and biomass production.
• Water mixing has to be constant during daylight hours in order to eliminate
microalgae stratification which leads to overexposure to solar irradiation to algae
close to the water surface and underexposure to algae below this upper layer.
Overexposure to solar irradiation causes a “light saturation” effect where all
microalgae light receptors are filled. When this occurs algae start to produce
pigments for protection from over-exposure to the sunlight. This consumes
energy that would have been used in reproduction. Pigment producing survival
mechanisms take over and production yields for biomass decrease and no omega-
3 is generated. Underexposure of algae to the sun simply reduces photosynthesis
and drastically reduces microalgae’s ability to reproduce. Water mixing can also
be used as a cooling mechanism by increasing mixing rate.
• Optimum water pH should be 6.8 - 7.2. This is controlled by regulating the
amount of CO2 that enters a microalgae pond. Higher concentrations of CO2
lower the pH which increases the acidity of the ponds.
• Black liners should not be used in open microalgae ponds because they increase
water temperature and reduce reflectivity of the pond’s bottom. These 2
conditions reduce biomass production yields.
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• An open pond microalgae farm should be located in a region with access to
saltwater, between the 30° North and South parallels for sufficient solar radiation,
and with very little or no rain precipitation. Rain has inhibitory effects which
reduces omega-3 production. Rain events reduce solar irradiation and therefore
biomass production. Rain also adds nitrogen containing freshwater to the ponds
which directly inhibits omega-3 formation. A cloudy or rainy day reduces
production yields between 30 and 50%.
The production yields in conventional open pond systems are predictable until
biological contamination occurs. One prevalent biological contaminant is a family of
aquatic micro-organisms called “rotifers”. Rotifers are medium sized multicellular
microorganisms (about 1000 cells) living mostly in freshwater or coastal habitats (Figure
6). Daily observations showed that contamination occurred when a new source of water
was used to compensate for pond evaporation (fresh or brinish water is added daily to the
system in order to maintain an appropriate salinity level). These contamination episodes
reduce useful biomass production by 50 to 80 %. Rotifers were suspected when the
lipid/protein composition of the biomass was analyzed after every event. Observations
under the microscope confirmed this suspicion.
58. 58
Figure 6. Picture of a “rotifer” micro-organism under the microscope (50X)
Water could be treated chemically or with ozone in order to get rid of rotifers, but
that will also kill the microalgae. Then the pond would have to be emptied, filled with
treated water and re-inoculated. This process takes 3 to 4 working days and production to
pre-contamination levels is re-established in 5 to 7 days. That is a big loss in overall
yield for the operation, considering that microalgae is harvested every day with a yield
ranging from 36 to 102 liters of omega-3 oil with 40 % EPA per hectare per day
(depending on the time of the year and weather).
Another way to kill the rotifers without killing the microalgae was developed by
understanding the physiology of this microorganism:
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• Rotifers have a life span of 3 to 4 days at 25°C, the same temperature that
optimizes algae production. Temperature could not be changed without
decreasing microalgae production levels.
• Rotifers require dissolved oxygen to survive and females lay eggs
approximately every 4 hours. Larvae become adult after 0.5 to 1.5 days in
order to re-start the reproduction cycle. This was a key factor used to develop
a system to eliminate rotifers without affecting the production yields for
microalgae.
Water for open ponds will be treated with ozone or other non-invasive systems
like ultraviolet radiation (UV rays). Then water in open ponds will be inoculated with
microalgae. Production will normally occur for a few days (5 or 6) and then the water
from that pond will be introduced in a photobioreactor (PBR). Carbon dioxide will not be
added so algae will reduce their metabolic rate and stop producing oxygen. The gas
exchange system will remove all the oxygen from the water inside the PBR, thus
eliminating all adult rotifers and their larvae. Water will remain anoxic for 5 to 12 hours
which eliminates all rotifer eggs. Meanwhile, the empty pond where contamination
occurred is cleaned with a low concentration chloride solution and exposed to the sun in
order to kill any potential rotifer residues. After less than a working day, water is
pumped out of the PBR and returned to the clean pond to resume regular production
operations. Overall yield losses are minimal or non-existent due to the fact that
microalgae growth is accelerated in a PBR, so all of the available CO2 dissolved in the
water was consumed and biomass was formed even with low metabolic rates.
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Dinoflagellates are marine plankton that also contaminate open pond systems.
They are mixotrophic but prefer to behave like algae predators. This predatory behavior
reduces biomass production rates and omega-3 production. A way to eliminate a
dinoflagellate outbreak is to increase water pH to 8.4 by adding sodium hydroxide and
stop all inputs of CO2 and nutrient into the pond. Due to a lack of nutrients (phosphates)
to feed on, the bacteria in their digestive tracks begin “eat” dinoflagellates from the inside
out.
Sustained production rates are approximately 15 to 20 grams/m2
. Plasma
gasification of 8129.3 Kg of biological waste produce 6958 Kg of CO2 which produce in
average 3760 Kg of algae biomass and 1500 Kg of omega-3 with EPA. Between 587 and
785 m2 of land are required to process the daily CO2 inputs from gasifying 8129.3 Kg of
biological waste annually.
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Chapter IV
Discussion and Conclusions
Description of the biological waste stream
The fact that biological waste contains infectious or potentially infectious
materials is well documented; however, the composition of biological waste is not well
characterized. On the other hand, municipal and chemical wastes have been well studied.
Municipal waste is variable due to the vast amount of materials that end up in trash. Even
with variation in composition studies have discovered that typical municipal wastes from
2010 contain 28% food waste, 18% yard waste, 24% paper, 22% plastics, 4% glass, and
4% metals (Habib, Schmidt, & Christensen, 2013). U.S. regulations require that chemical
wastes be characterized so that percentages of all components are known at all times.
Important decisions regarding the treatment of municipal or chemical waste are better
made knowing the composition of the waste that is collected. This allows for more
efficient management of resources to minimize environmental, social and financial
impacts. Biological waste streams contains a mixture of paper, plastic, metal, glass and
biogenic materials believed or known to be contaminated with infectious materials.
However, there is no information available which accurately describes the composition of
biological waste. The term biological waste describes a type of waste commonly known
by various other names such as biohazardous waste, medical waste or infectious waste.
This type of waste contains or potentially contains materials that may be infectious to
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healthy humans and therefore must be kept secure until final destruction renders the
waste non-infectious. Various industries, such as healthcare, higher education and the
life sciences, generate biological waste. The composition of biological waste changes
depending on the activities being performed at the site of waste generation. Healthcare
institutions generate significant amounts of: contaminated materials that have come into
contact with patients, disposable materials such as IV bags, and materials contaminated
with drugs such as chemotherapeutics and pain medications excreted or unused by
patients. Biotechnology research generates much less waste containing tissue or body
fluids and more waste contaminated with laboratory scale cell culture. Biotechnology
research is focused on the manipulation of a biological system to achieve a predictable
outcome. Many innovations involving human immune modulations have advanced
healthcare therapies targeting Severe Combined Immune Deficiency, Chronic
Granulomatous Disorder, Hemophilia, and various cancers and neurodegenerative
diseases. Human therapeutic research involves using human blood, cell lines and tissue
samples for laboratory scale manipulation. Successful research programs involve animal
research which generates various animal tissue and body fluid samples as waste. The
various activities involved in research with human and animal materials generates a large
amount of contaminated single use equipment. Also known as consumables, this
equipment includes: pipette tips, serological pipettes, cell culture flasks, and nitrile work
gloves.
To properly conduct a life cycle assessment comparing regular incineration and
plasma gasification, an accurate description of the make-up of biological waste is
63. 63
necessary. Studies indicate that sharps materials such as syringes, needles, scalpels, glass
tubes, microscope slides, and broken glass are present in the biological waste stream
(Mecklem & Neumann, 2003). The United States Environmental Protection Agency
characterizes biological waste to include: cultures and stocks of infectious agents, human
blood and blood products, human pathological wastes (including those from surgery and
autopsy), contaminated animal carcasses from medical research, wastes from patients
isolated with highly communicable diseases, and all used sharp implements (such as
needles and scalpels) and certain unused sharps (U.S. Environmental Protection Agency,
1989). Sampling of biological waste containers from a biotechnology research company
in Cambridge, MA, indicated that 80% percentage of biological waste is composed of
single use plastic materials (Appendix 4). The remaining materials are paper, cardboard,
and biogenic. It is important to note that glass and metals (e.g., needles) are present in
very small percentages but they are not captured in our assessment since we are focusing
on organic materials that are combusted during disposal. The maximum allowable weight
of one full biological waste container due to Department of Transportation shipping
container requirements is 22.7 kg (50 lbs). The average weight of a full container in our
study was approximately 7.2 kg (15.9 lbs). The fact that the average weight was less than
half the maximum allowable weight indicates that there is a very low density of materials
in the biological waste containers. Our observations indicated that a large amount of
empty but contaminated plastic containers were disposed of into the biological waste
stream. Additionally, a significant amount of paper and plastic packaging materials were
also observed in the biological waste containers (Figure 7).
64. 64
Figure 7. Images of the inside of biological waste containers showing various plastic and
paper waste materials.
Knowing the basic composition of biological waste is important if a waste
manager is expected to run an efficient disposal program that minimizes waste. Poor
laboratory practices and training may contribute to an increase in the collection of non-
contaminated materials as regulated biological waste. For example, Figure 7 shows
empty media and buffer solution bottles in a waste container. Proper lab practices should
have allowed these bottles to remain contamination free. This indicates that there is a
high percentage of laboratory waste that should be recycled or reused.
65. 65
Waste Disposal Technology Selection
While incineration is a readily available and accepted disposal option for the
destruction of waste materials, it adversely impacts human health and the environment.
These harmful impacts have driven our waste management industry to identify and
implement numerous technologies that are much less damaging than incineration. Some
biogenic waste disposal activities include composting, anaerobic digestion, biochar
production, and conversion technologies that can generate ethanol or biodiesel (Vergara
& Tchobanoglous, 2012). These methods are effective at managing organic waste
materials with minimal inputs and minimal environmental and human health impacts.
However, they require well segregated organic wastes and specialized facilities that are
not available on a commercial scale (Vergara & Tchobanoglous, 2012). In a fast paced
biotechnology research facility, managers must make decisions about how to organize
waste streams and communicate the waste management strategy to employees. This
requires additional floor space and containers as well as time for additional training
which can become a burden that company leaders may find unacceptable. Therefore more
manageable, non-biogenic strategies seem to be popular for biotechnology waste
management. Some non-biogenic activities include incineration, plasma gasification,
pyrolysis, and recycling (Vergara & Tchobanoglous, 2012).
Recycling facilities are not qualified to destroy infectious materials. Pyrolysis
technology is not helpful since it requires biomass waste which typical biological waste
does not contain at a high level (Figure 7). Depending on the actual contents of biological
waste, a waste manager may decide that the waste should be disinfected via an autoclave
66. 66
prior to final disposal in a landfill. Autoclaving is effective at sterilizing most biologicals
but the contaminated waste debris are not destroyed and continue to take up a larger
volume of space. Alternatives to landfills have been pursued since 1903, when Denmark
built the first incineration plant due to a lack of landfill space (Habib, Schmidt, &
Christensen, 2013). Since that time we have learned that landfills are a primary source of
methane, a harmful and powerful greenhouse gas (Vergara & Tchobanoglous, 2012). The
United States Department of Health and Human Services requires that pathogenic
materials, such as prions, be destroyed by using incineration only (United States
Department of Health and Human Services, 2009). Standard disinfection techniques, such
as autoclaving, irradiation, boiling, dry heat and chemicals (formalin, alcohols,
Betapropiolactone), are not effective at inactivating prions (United States Department of
Health and Human Services, 2009). Incineration is effective at destroying all biological
materials, including prions, due to high furnace temperatures. The resulting ash is
landfilled as the final step of incineration.
Incineration is a commonly used technology that effectively destroys biologicals
and minimizes the volume of landfill waste. Modern incinerators can be designed to
process varying types of waste, are characterized by emissions abatement and pollution
prevention systems and use various types of combustion technologies (Marchettini,
Ridolfi, & Rustici, 2006). The practice of using incineration as a disposal method has
been heavily scrutinized for its harmful impacts on human health and the environment.
Health issues are directly (via occupations in the industry) and indirectly (e.g., via
ingestion of contaminated food, water, and soil) associated with all steps of waste
67. 67
management (Giusti, 2009). The environmental impacts of incineration can be wide
ranging but generally impact water fall-out of atmospheric pollutants, air (SO2, NOx,
N2O, HCl, HF, CO, CO2, dioxins, furans, PAHs, VOCs, odor, noise), soil (fly ash and
slags), landscape (visual effect) and the climate (generation of greenhouse gases) (Giusti,
2009). As indicated by Appendix 9, human health and the environment is more
negatively impacted by the use of incineration. Incineration has been shown to adversely
impact human health by increasing the incidence of cancer and congenital birth defects
(Forastiere, et al., 2011). A review of health effects related to incineration indicated that
studies conducted from 1983 and 2008 provided evidence of increased risk for various
types of cancer (stomach, colorectal, lung, liver, soft-tissue carcinoma, non-Hodgkin’s
lymphoma) and congenital malformations (facial cleft, renal dysplasia) (Porta, Milani,
Perucci, & Forastiere, 2009).
Additionally, there are documented health effects linking landfills to an increased
risk for congenital malformations (neural tube defects, hypospadias, epispadias,
abdominal wall defects, gastroschisis, exomphalos) and very low birth weight (Porta,
Milani, Perucci, & Forastiere, 2009). While specific linkages between pollutants and
cancer or congenital malformations were not identified, exposure to dioxins has been
suggested as a primary causative agent (Porta, Milani, Perucci, & Forastiere, 2009). It has
also been established that landfills generate a significant amount of methane, a powerful
greenhouse gas estimated to be 21 times more potent than CO2, which is the leading
contributor from the waste management industry to climate change and global warming.
In Europe, methane from landfills accounts for 1/3 of the anthropogenic emissions while
68. 68
CO2 and N2O, both significant contributors to global climate change, account for only 1%
and <0.5% of emissions respectively (Pikoń & Gaska, 2012). Landfills remain the most
widely used waste disposal activity however political and financial factors are beginning
to require that landfilling be the last step of waste disposal, after all possible material and
energy recovery has taken place. Landfilling has been identified as a disposal method that
is significantly more costly due to high and prolonged operational costs and low energy
and materials recovery (Marchettini, Ridolfi, & Rustici, 2006).
We show that incineration and landfilling significantly contribute to an increase in
human disease and negative environmental impacts, whereas plasma gasification
combined with gas capture and sequestration has been shown to mitigate these
destructive factors (Appendix 9). The extremely high temperature of plasma gasification
obliterates all chemical pollutants leaving syngas, a valuable material that will be
recovered. This process also generates slag, the inorganic, inert, glasslike material that
can be either reused or harmlessly disposed on in an inert landfill due to its low
leachability (Gomez, et al., 2009). The LCIA results for the incineration (Appendix 5)
and autoclaving/landfilling (Appendix 6) of biological waste show a greater negative
impact on climate change and human health than those from plasma gasification
(Appendix 7). Landfilling of biological waste (Appendix 4) does not significantly
contribute to these negative effects since much of the waste is relatively inert. However,
since biological waste is disinfected via an autoclave prior to landfilling, a high amount
of energy is consumed to generate the temperatures and pressures necessary for
disinfection. The energy needed for this activity is generated by fossil fuel burning power
69. 69
plants. The fossil fuel combustion combined with the inherent risks created by depositing
waste into landfills are the main contributors to the LCIA categories for climate change,
human toxicity, freshwater ecotoxicity, and marine ecotoxicity (Appendix 6). LCIA
results from plasma incineration of biological waste show that the categories related to
human health and environmental impacts are minimal and indicate that the complete
destruction of organic pollutants and the capture of inorganic pollutants in slag mitigate
most of the harmful impacts created when incinerating or landfilling/autoclaving
biological waste (Appendix 9).
A Stable Source of Carbon Dioxide
The amount of CO2 generated by the plasma gasification of biological waste
produced by a biotechnology research company with 300 employees and approximately
100,000 ft2 of lab space is sufficient for the production of about 3760 Kg of algae
biomass and 1500 Kg of omega-3 with EPA. As of August 20, 2014, the state of
Massachusetts has 738 biotechnology and pharmaceutical establishments which accounts
for approximately 21 million square feet of lab space and 57,000 employees
(Massachusetts Biotechnology Council, 2014). When square footage of lab space is used
to virtually scale up microalgae production, 789,600 Kg of algae biomass and 315,000
Kg omega-3 with EPA is generated. It is difficult to verify these figures by using such a
correlation since each company differs in the type of research activities and materials that
are utilized. However, it is relevant for the purposes of establishing the potential impact
of using biological waste for the large scale production of microalgae.
70. 70
California is a leading state in the biotechnology industry with employment at
approximately 24,000 for research and development and 45,000 for manufacturing
(Massachusetts Biotechnology Council, 2014). The selection of Southern California is
helpful due to the concentration of biotechnology research institutions in and near San
Diego and Los Angeles. Southern California counties, consisting of Los Angeles, San
Diego, Orange, Riverside, and San Bernardino, account for 59% of the total
biotechnology employment in the State of California (Gollaher & Claude, 2014). Not
only is Southern California is an attractive location for our proposed system due to the
abundance of biological waste sources but also for its proximity to 30° North latitude and
seawater, its lack of rain, and the availability of non-arable land.
The characterization of biological waste from a biotechnology research company
had not been previously established. After characterizing biological waste it became clear
that there are many similarities in basic composition to municipal solid waste. General
categories of waste materials commonly found in municipal solid waste are plastic, metal,
glass, paper, and organic. While the composition of municipal solid waste differs by
location it continues to be composed of the same basic materials. On a global level
developing nations have more organic materials and developed nations have more
complex waste compositions (Appendix 12). The waste fractions that we are targeting in
our gasification process are organic and the abundance of organic materials that exist in
municipal solid waste indicate that this waste stream would be a suitable candidate from
which CO2 can be collected for algae farming. One study calculated that greenhouse gas
emissions from solid waste disposal in Europe contributes <0.5% CO2, 33% CH4, and
